Shield assembly for high-voltage gas circuit breaker

ABSTRACT

A high voltage gas circuit breaker has a plurality of interrupter structures, each of which contain an upper stationary contact and corona shield which surrounds the upper contact. The corona shield has openings in a lower rim disposed to direct the gas blast during interruption downwardly and at an angle outwardly from the external surface of its respective interrupter structure from the external surface of its respective interrupter structure to prevent contamination of the insulation surface of the interrupter structure by arc products.

United States Patent Inventors Henry G. Meier Glendale;

James R. McCloud, Burbank, both of Calif. Appl. No. 852,535 Filed Aug.25, I969v Patented Oct. 19, 1971 Assignee I-T-E Imperial CorporationPhiladelphia, Pa.

SHIELD ASSEMBLY FOR HIGH-VOLTAGE GAS CIRCUIT BREAKER 7 Claims, 6 DrawingFigs.

0.8. CI 200/148 R, 200/ 148 IV Int. Cl HOIh 33/82 Field of SearchZOO/148.2, 148 B, 148

[5 6] References Cited UNITED STATES PATENTS 3,040,149 6/1962 Easley etal 200/148 B 3,495,057 2/l970 Golota 200/148 B Primary Examiner-RobertS. Macon Attorney-0strolenk, Faber, Gerb & Soffen ABSTRACT: A highvoltage gas circuit breaker has a plurality of interrupter structures,each of which contain an upper stationary contact and corona shieldwhich surrounds the upper contact. The corona shield has openings in alower rim disposed to direct the gas blast during interruptiondownwardly and at an angle outwardly from the external surface of itsrespective interrupter structure from the external surface of itsrespective interrupter structure to prevent contamination of theinsulation surface of the interrupter structure by are products.

PATENTEUHBT 19 ml 3.614.356

- SHEET 5 [IF 5 SHIELD ASSEMBLY FOR HIGH-VOLTAGE GAS CIRCUIT BREAKERRELATED APPLICATIONS This application is an improvement of the structureshown in copending application Ser. No. 680,778, filed Nov. 6, 1967, inthe name of John H. Golota, and assigned to the assignee of the presentinvention. This application is related to copending application Ser. No.845,375, filed July 28, I969, in the name of Henry G. Meier and James R.McCloud, and assigned to the assignee of the present invention.

THE PRIOR ART Circuit interrupters of the type to which the inventionapplies are known and are typically shown in the above-notedapplication. Such interrupters are provided with a stationary nozzlecontact and a movable contact which is surrounded by a movable bafflewhich can engage the stationary nozzle contact to define a confined gasblast path through an arc drawn between the movable and stationarycontacts during their separation. A blast valve which is upstream of thecontacts is opened just prior to the opening of the contacts. The baffleis adapted to be withdrawn when the contacts are fully opened and thegas blast is turned off to bring it out of the high electrostatic stressregion between the opened contacts.

In the past, the gas blast has been directed downwardly and over theouter surface of the insulation members forming the interruptionchamber. It has been found that this can cause the coating of theseinsulating surfaces with conductive contamination products, therebyreducing the ability of the interrupter to withstand high voltage whenthe interrupter is open.

The present invention forces the gas blast during arcing to be directeddownwardly, but angled away from these insulation surfaces so that thehigh voltage withstanding ability of the interrupter is not affectedafter prolonged operation.

SUMMARY OF INVENTION Inaccordance with the present invention, the coronashield for each of the interrupters is provided with one or moreopenings along a bottom inwardly turned lip thereof, with the interiorof the shield being in communication with the interior of the nozzle ofthe stationary contact. The openings in the shield are spaced outwardlyfrom its interior diameter so that gas during interruption is forced totake a path downward but flaring outward at an angle of, for example, 30from the axis of the interrupter chamber, whereby the gas duringinterrup tion is not applied directly onto the outer surface of theinterrupter chamber.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows a circuit breaker of thetype to which the invention applies, and is partly in cross section.

FIG. 2 is a cross-sectional view of tone of the interrupters of FIG. 1.

FIG. 3 is a cross-sectional view of the novel structure of the presentinvention.

FIG. 4 is a cross-sectional view of a portion of one interrupter of thetype shown in FIG. 3 along with a corona shield providing dischargeopenings in accordance with the invention.

FIG. 5 is a cross'sectional view of FIG. 4 with the left-hand side ofFIG. 5 being taken across the section lines 5a-5a in FIG. 4 and with theright-hand side of FIG. 5 being taken across the section lines 5b-5b inFIG. 4.

FIG. 6 schematically shows a schematic diagram of a complete circuitinterrupter in cross-sectional view and illustrates the gas blastpatterns for each interrupter in accordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS a. Background of the InventionFIGS. 1 and 2 show a typical prior art interrupter structure to whichthe present invention is applied. The device of FIGS. 1 and 2 is shownin copending application Ser. No. 680,778, and the disclosure of thatapplication is incorporated herein by reference to show the entirecircuit breaker assembly which would be used with the present invention.

FIG. I shows the assembly of a prior art interrupter assembly, andillustrates two series connected interrupters l0 and 11. Interrupters l0and 11 are identical and will be described in detail hereinafter. Theinterrupters I0 and II are controlled by an operating mechanism,generally indicated by numeral 12, which is supported on a tank housing13. Tank housing 13 is, in turn, carried on an elongated insulationpedestal 14 which may be carried on a high-pressure gas supply at groundpotential.

Each of interrupters 10 and 11 are connected at their tops to conductorswhich are connected in series with the circuit to be protected. Theconnection surrounding the topsof interrupters l0 and 11 and theinsulator bushings are covered with corona shields l5 and 16. FIG. 2shows the connection of interrupter 10 to a lower portion 17 of aninsulator bushing connected thereto.

An upper adapter plate 18 is provided which has a series of tappedopenings therein, and alternate through-openings (not shown). The uppersurface of adapter 18 then has a conical surface 31 which engages theconical lower surface 32 of insu lator 17 to permit angular adjustmentof insulator 17, as shown by arrow 17a in FIG. 2. A series of bolts,such as bolt 33 having washer 34, then extend through openings, such asthrough-opening 28, to secure upper adapter 18 to insulator I7.

A lower adapter 35 is then provided which has a plurality of extendingears containing through-openings such as opening 36 extending from acentral web 42. An annular groove 43 is cut through the web 42 so thatit is held by the material of the extending cars. A plurality ofthrough-holes and aligned tapped openings such as opening 44 are thenformed in the web 42, and the interior web surface is threaded by thread50. The through-openings in lower adapter 35 are then aligned withtapped openings in upper adapter 18 and suitable bolts and washers, suchas bolt 51 and washer 52, shown in FIG. 1, secure shield 15 and adapterplates 18 and 35 together.

The interior thread 50 of web 42 of lower adapter 35 receives thestationary contact 53 of the interrupter. Contact 53 comprises a mainbody 54 having a central opening 55 which tapers outwardly to define ablast orifice. The outer diameter of body 54 is threaded with a thread56, and an arcresistant insert 57. Thread 56 of contact 53 is thenthreaded into thread 50 of lower adapter 35 and is secured therein bytightening a plurality of bolts, such as bolt 570, shown in FIG. 2,which pass through the through-openings in the lower part of web 42 andinto the threaded opening 44. As these bolts are tightened, the upperand lower interior portions of web 42 tighten on thread 56 to holdcontact 53 securely. Note that the axial contact position is easilycontrolled by threading contact 53 more or less into thread 50, as shownby arrow 58 in FIG. 2. Moreover, by providing clearance between theouter diameter of the bolts, such as bolt 51, which secure lower adapter35 to upper adapter 18 and the corresponding through-openings, such asopening 36, lateral adjustment can be obtained for contact 53, as shownby arrow 59 in FIG. 2.

The movable contact assembly is shown in FIG. 2 and is composed of acircular cluster of contact fingers, such as fingers 60 and 66, eachhaving generally rectangular shape. Each of the contact fingers havearc-resistant inserts secured thereto, such as inserts 72 and 73,secured to contacts 60 and 66, respectively. Each of the contact fingershave two projections, such as projections 74 and 75, for finger 60,which receive biasing leaf springs shown as leaf springs 76 and 77 forcontacts 60 and 66 which bear on insulation buttons 78 and 79,respectively.

The contact fingers are-laid on the outer notches in a contact retainer80, and are held on the retainer 80 by a spring and to providecommutation of the are from insert 72 to contact 85 during opening. Theinterior of arcing contact 85 is threaded and threadably receives theend of operating shaft 86 and is secured thereon by a suitable lockingnut.

An interrupter support 88 is then provided for slidably holding themovable contact assembly. Support 88 contains a central stationarycontact portion 89, the outer end of which slidably receives the lowerends of contact fingers, such as fingers 60 and 66, in slidableengagement. Central portion 89 is connected to base portion 90 bysuitable webs (not shown). Two rings 107 and 108 of insulating material,shown in FIG. 2, are contained in internal grooves in the centralopening 111 of central portion 89 to seal around the operating rod 86and to provide electrical insulation between rod 86 and base 90, asshown in FIG. 2. Support 88 is then fastened to support casting sections112 and 113 (which are parts of a common casting) of FIGS. 1 and 2, asby bolts which thread into appropriate tapped openings in castingsections 112 and 113, partly shown in FIG. 1 by bolts 114 and 115. Notethat the operating rod 86 passes through a suitable opening, which maybe sealed, in casting section 112. I

An interrupter tube assembly, arranged above the support 88 andenclosing the contact area is carried on a flange 116. Flange 116comprises an extending cylindrical portion 117 secured to support 88beneath it by bolts (not shown) extending through openings in flange 116and respective openings in support 88, which bolts are threaded into thecastings 112 and 113.

An interrupter tube 122 is then secured to extension 117 in any suitablemanner, where tube 122 is of glass fiber, or the like. Tube 122 thenslidably receives the movable interrupter tube portion (or baffle) 123,which is movable in the direction of arrow 124, with a gasket 125abetween the surfaces of tube 122 and sliding portion 123.

The movable interrupter tube or baffle 123 comprises an outervinsulation cylinder 125 and an inner lining cylinder 126 which secure,between them, an insulation lining disk 127 and baffle ring 128. Thebottom of the cylinders are secured by ring 129 which has a lower lipextending below liner 126 and a plurality of pins, such as pin 130,which extend into cylinder 125.

Four pins, two of which are shown as pins 131 and 133, then extend intoopenings in ring 129 and are locked therein by suitable locking pins.Pins 131 and 133 are seen in FIG. 2 with the four pins disposed 90 fromone another. Each of the pins have enlarged heads, such as head 135 ofpin 133, which are captured in housings, such as housing 138 for pin133. A split retainer spring disk 139 has suitable openings forreceiving the four spring housings, including housing 138. Internalsprings, such as spring 145 of housing 138, then bias the housingstoward the ring 129 and external springs, such as spring 148, bias plate139 toward the ring 129.

In assembling the movable interrupter tube, it will be noted in FIG. 2that the periphery. of plate 139 is captured between adapter 116 andsupport 88, with ring 129 beneath shoulder 150 in stationary tubeportion 122. Also, it is seen that the baffle ring lies just adjacentthe lower tapered surface of contact 53.

The operating mechanism for moving operating rod 86 is best shown inFIG. 1 where it is seen that the casting sections 112 and 113 have adownwardly extending portion 151. For tion 151 has two slots for passingears 152 and 153 of a cylindrical blast valve. The cars 152 and 153 arethen connected to links 154 and 155, respectively, which are, in turn,pivotally connected to operating rods 86 for interrupters 10 and 11through suitable couplings 156 and 157, respectively.

The blast valve comprises a cylindrical body 158 connected to a centralhub 159 by streamlined arms, such as arm 160. The ends of cylindricalbody 158 are formed with annular valve disk engaging sections. Theinterior opening in hub 159 is provided with a thread 166. The two ears152 and 153 then extend outward from cylindrical body 158.

Cylindrical valve body 158 then moves between an upper and lower valveseat. The upper valve seat is composed of an upper disk 167 which issecured to casting section 113 and a lower disk 168 which is bolted todisk 167 as by bolts, such as bolt 169. Disk 168 is sealed with respectto casting section 113 by seal ring 170 and carries a main valve seatring 171 which cooperates with the upper end of cylindrical valve body158. A valve retaining disk 172 is bolted to disk 168 as by bolt 173 andsecurely holds ring 171 in position. Disk 172 also has a buffer disk 174bolted thereto as by bolt 175 which engages nut 176 when the valve 158is moved upwardly.

Hub 159 is threaded on operating shaft 177 and is locked in place by nut176 which is also threaded on shaft 177. Note that an annular seal 178is contained in casting portion 112 and seals around cylinder 158 andguides the motion of cylinder 158.

A ring 180 is then secured to the bottom of casting 112, and downwardlyprojecting members 181 are welded to ring 180.

-Members 181 then support the lower valve seal for valve 158.

Note that a ring 182 having a sealing ring 183 engaging ring 182 isprovided with a sliding seal ring which surrounds the lower portion ofcylinder 158.

The bottom of members 181 carries a ring 185. Ring 185 is connected tovalve disk 186 and valve disk 187 by bolt means, such as bolt 188.Sealing rings 189 and 190 prevent leakage between rings 185 and 186.Ring 186 carries a main valve seat 191 which cooperates with the bottomof cylinder 158. Note that a sliding seal 192 is formed between disk 186and shaft 177, and that a buffer 193 is connected to the top of disk 187to receive the bottom of hub 159 when valve 158 moves down.

The ring 180 is welded to high-pressure tank 13 which is composed ofwelded upper and lower halves 200 and 201, respectively. High-pressuregas, such as air and preferably sulfur hexafluoride, is then supplied tothe interior of tank 13 from the central channel through insulator 14which is appropriately connected at its bottom to a high-pressure gassource, as will be later described.

' An elongated operating shaft 203, which extends coaxially withinsulator 14, can be moved up and down by operating means, to be laterdescribed, which may be carried at ground, and is connected to shaft 177by a shock-absorbing coupling.

FIG. 1 further shows a small tubular member extending downwardly andinto the annular space between pedestal 14 and rod 203, and arranged sothat any gas which condenses on the surface of housing 13 will flowdownwardly and freely through the annular space without impinging on theinsulating surfaces of members 14 and 203.

The coupling as shown in FIG. 1 is comprised of a spring 204 capturedbetween rings 205 and 206 at its top and bottom, and an outer cylinder207 on its outer periphery. Ring 205 is captured beneath a shoulder inshaft 177 as shown, while ring 206 is held by nuts 208 and'209 which arethreaded on the threaded'bottom of shaft 177. Outer shells 210 and 211each have threaded interiors, threaded on the outer threaded surface ofcylinder 207 with extension 212 of shell 210 bearing on ring 205, whilering 206 seats under the interior shoulder in cylinder 207. Operatingshaft 203 is then connected to shell 211 by connection ring 213. Whenshaft 203 moves down, it will be seen that downward force is exertedthrough shells 211, 210, ring 205, and spring 204 on ring 206.Similarly, upward movement of shaft 203 is transmitted through cylinder207, ring 206, spring 204 and ring 205. Thus,

. both upward and downward movement of shaft 203 is transmitted to shaft177 through shock-absorbing spring 204. This also makes the mechanismrelatively insensitive to small dimensional changes such as produced bymisalignment and temperature changes.

OPERATION OF PRIOR ART DEVICE OF FIGS. 1 AND 2 The prior art device ofFIGS. 1 and 2 operates such that interrupter tube 123 is biaseddownwardly to an open position by spring 145 when the movable contactstructure is open. When the circuit breaker is closed, the movablecontact moves up and the upper end of insert 72 picks up the movabletube or-baffle 123 at liner 127 and drives the baffle against and aroundthe stationary contact 53. This then defines a channel for movement ofhigh-pressure gas through the interior of baffle 123 and out through theopening 55 in contact 53, and thus through the separating contacts.

When the circuit breaker is to be opened, operating rod 203 moves downto open valve 158, permitting the flow of highpressure gas into theinterior of the interrupter and the interior of baffle 123. Note thatthe pressure of this gas holds the baffle 123 closed against the forceof its opening biasing springs even though the movable contact movesdown and away from baffie 123. Thus, the desired gas passage for movinggas through the orifice 55 is maintained by baffle 123.

Once the valve 158 reaches valve 191, the contacts are fully open andthe arc extinguished. The gas pressure is removed from baffle 123 sothat it is moved downward to an open" position by its biasing springs sothat it removed from the high stress of the electrostatic field in theregion between the open contacts.

It is seen that the baffle 123 is driven closed by the movable contact(or is closely followed by the movable contact) when this contact isclosed, and is held in its closed position. It has been found that thehigh-impact forces on the baffle from the movable contact can break thebaffle 123.

THE STRUCTURE SHOWN IN FIG. 3

The present invention provides an improved drive for baffle 123 in whichit is operated solely by differential pressure operating against thebiasing force of the baffle opening springs so that the baffle 123 isnot subject to breakage due to impact with the movable contact. Theinvention is shown-in FIG. 3 in which parts similar to those of FIGS. 1and 2 have similar identifying numerals. A few further differences,besides the change in the essential baffle structure are also shown inFIG. 3, and will be discussed. In FIG. 3, the structure to the left ofthe centerline is shown in section with the baffle 123 open and thecontacts closed. The movable contact is shown in plan view to the rightof the centerline with the movable contact in its open position.

The interrupter of FIG. 3 corresponds to interrupter of FIGS. 1 and 2,and it is seen that lower adapter plate 35 receives contact 53. Themovable contact assembly 300 is similar to that of FIG. 2, but ismodified in a few respects. Thus, typical contact 301, corresponding tocontact 66 of FIG. 1 has an integral arcing surface 302 for engagingcontact 53. Note that finger contacts 303, 304 and 305 are partly shown,in the open position to the right of the centerline in FIG. 3. Inaddition, a circular conductive shield 306 is secured to the variouscontact finger biasing springs and cooperates with member 81 in FIG. 2.Arcing contact 85 is attached to rod 86 by a modified flanged body 310in FIG. 3. In addition, a modified buffer 311 is secured to member 89 toreceive the bottom of member 310 when the movable contact reaches theopen position.

In FIG. 3, a unitary sleeve 312 bolted to body 88 replaces flange 117and member 122 of FIG. 2, where sleeve 312 has a larger diameter thanmember 122 of FIG. 2 to accommodate a larger diameter baffle 123.

Baffle 123 has a shortened inwardly turned lip 313, the interiordiameter of which is greater than the outer diameter of contact shield306. Thus, as contrasted to the arrangement of 7 FIG. 2, the movablecontact assembly will not engage baffle 123. Baffle 123 then has ininterior liner 314, and the baffleis secured to a lower plate 315 by aclamp 316. Plate 315 receives a plurality of bolts, such as bolt 317,about its periphery which have extending heads such as head 318. Springhousings, such as housing 311 in FIG. 3, are pressed against plate 315by springs, such as spring 320, partly shown in FIG. 3, which pressesbetween head 318 and the top of the tube 311. Tube 311 is then biasedagainst fixed plate 321 by spring 322 contained in spring guide tube323. As in the case of FIG. 2, a plurality of such spring supportelements are disposed around the periphery of plate 315, and operatenormally to bias baffle 123 downward to the open position shown in FIG.3 (through compression springs such as spring 320).

OPERATION OF DEVICE OF FIG. 3

In operation, when the contacts are closed, as shown to the left in FIG.3, the baffle 123 will be open due to the biasing springs, such asspring 320, which bias baffle 123 downwardly. If the breaker is to beopened, rod 86 is moved down, and, as shown in FIGS. 1 and 2, the blastvalve 158 is opened. A highpressure gas then flows upwardly in thedirection of arrow 330, thereby applying a differential force to baffle123 which moves the baffle upward and against springs such as spring320. The baffle 123 then closes against a seal 331 formed in contact 53,thereby defining a gas flow channel through orifice 55. The contactssubsequently separate and this gas flows in the region of the arc tocool and deionize the arc. When the movable contact reaches its fullyopen position shown to the right of the centerline in FIG. 3, the blastvalve closes and the high-pressure gas is cut off. Thus, baffle 123retracts to its open position and away from the gap between the opencontacts.

When the breaker is to be closed, rod 86 is moved upward and the blastvalve is again opened. High-pressure gas thus flows to temporarily closebaffle 123 to form the desired gas channel through orifice 55. After thecontacts are closed, the blast valve closes, and baffle 123 retracts toits open position. Note that in the above operation, the movable contactdoes not engage baffle 123 and any overtravel of the movable contactwill not affect the baffle 123. Moreover, and as shown in FIG. 3 to theright of the centerline, the baffle 123 is disposed in its mostfavorable dielectric position when the contacts are open with itsinwardly facing lip 313 generally parallel to the end of arcing contact57. Thus, the baffle 123 generally follows an equipotential line in theopen contact gap, and is subject to minimum dielectric stress.

THE INVENTION SHOWN IN FIGS. 4, 5 AND 6 The invention is shown inconnection with the interrupter structure of the type described in FIG.3, and consists of the modified corona shield structure 401 shown inFIGS. 4 and 5. Corona shield 401 is suitably connected to adapter 402(which may be similar to adapter 18 of FIG. 1) through a spider plate399. The spider plate 399 is provided with spider sections such assections 403, 404, 405 and 406, as shown in FIG. 5. The spider plate 399is connected to adapter 402 as by volts, such as bolt 407, and is alsoconnected to the stationary contact by bolts, such as bolts 408 and 409.

In accordance with the present invention, corona shield 401 has aninwardly turned bottom section 398 which contains a plurality ofopenings, such as openings 410, 411, $12, 413 and 414; opening 413 beingshown in both FIGS. 4 and 5. Each of the openings such as 410 to 414 lieon a circle having a diameter greater than the outer diameter of member312 and are angled outwardly from the centerline of the interrupter.Accordingly, during interruption, gas will flow as indicated by arrows420 and 421, where the gas emerging from the shield the interrupters andcapacitors. It will be noted that this is a distinct advantage from thearrangement shown in FIG. 1, for example, where the are products aredischarged from shields 15 and 16 directly down and over the exterior ofinterrupters l and 11. FIG. 6 schematically illustrates the blastpattern for an entire circuit breaker. Thus, in FIG. 6 there isschematically illustrated four corona shields 430, 431, 432 and 433 offour series-connected interrupters contained within a comand orifices433a and 433 b for shield 433. It will be seen that the orifice lengths(of the equivalent orifice fonned by a plurality of individual openings)is such that the blast from one interrupter is not discharged againstthe exterior surface of an adjacent interrupter. Thus, in FIG. 6 theorifices are so dimensioned that the blast is downward and at about 30from the center line of the respective interrupters. In this manner, thedischarge gas of the interrupters cannot cause flashover to the groundedtank during interruption or adversely'coat the interior of the tankwalls which are sufficiently spaced from the interrupters. Shields 430and 433 are of the type shown for interrupter 11 in FIG. 1 and for theinterrupter shown in FIGS. 4 and 5. Shields 431 and.432 aremodifications of the shield shown in shield in FIG. 1.

In the event that voltage grading capacitors are connected across thevarious interrupter contacts, these capacitors can be so located on theexteriorof the interrupter that they are out of the path of the blastgas. Thus, capacitors can be located alongside each interrupter atlocations schematically shown in FIGS. 5 and 6 by pairs of gradingcapacitors 500-501 (FIG. 5); and 502-503, 504-505, 506-507 and 508-509for the four interrupters of FIG. 6. Note that the coating of thesecapacitors by blast products would short circuit the interrupter so thatthey must be out of the blast gas path.

'Although this invention has been described with respect to particularembodiments, it should be understood that many" variations andmodifications will now be obvious to those ,skilled in the art, and,therefore, the scope of this invention is limited not by the specificdisclosure herein, but only by the appended claims.

The embodiments of the invention. in which an exclusive privilege orproperty is claimed are defined as follows:

1. In a gas blast circuit interrupter; said gas blast circuitinterrupter comprising a stationary contact having a central channeltherethrough, a movable contact movable into and out of engagement withrespect to said stationary contact, a'

source of high-pressure gas, a hollow cylindrical valve of insulationmaterial surrounding said movable contact'and being movable into and outof sealing relation with an annular area surrounding said centralchannel, means connecting said source of high-pressure gas to theinterior of said hollow cylindrical valve, means for moving said hollowcylindrical valve out of sealing relation with said annular area whensaid movable contact moves out of engagement with said stationarycontact, whereby a blast of gas is directed between said movable andstationary contacts and through said central channel in said stationarycontact, and a corona shield comprising a smoothly curved, generallyhollow cylindrical conductive body surrounding said stationary contact,one end of said corona shield being in a plane generally adjacent theend of said stationary contact and having an inwardly turned rimportion; the improvement which comprises gasdischarge opening means insaid inwardly turned rim portion which are disposed outwardly from theinterior diameter of said rim portion and gas channel means forconnecting said central channel in said stationary contact to saiddischarge opening means; the discharge path of all 'gas dischargedthrough said discharge opening means extending at an angle to the axisof said hollow cylindrical valve and being directed away from the outersurface of said hollow cylindrical valve.

2. The interrupter of claim 1 wherein the outer diameter of said hollowcylindrical valve is about equal to the internal diameter of saidinwardly turned rim portion of said shield.

3. The interrupter of claim 2 wherein said discharge opening meansconsists of a plurality of spaced openings in said rim.

4. The interrupter of claim 2 which includes a second interrupter ofsimilar construction positioned adjacent thereto, and a tank forreceiving said interrupter and said second interrupter; said dischargeopening means of the corona shields of said interrupters defining blastpatterns extending generally laterally of a line joining saidinterrupters to prevent the application of the gas blast of one of saidinterrupters to the hollow movable valve of the other.

5. In a high-voltage gas blast interrupter;

" a. a stationaryv contact assembly having a gas discharge channeltherethrough;

b. a tubular interrupter assembly presenting an outer insulation surfacewhich is coaxial with said gas discharge channel in said stationarycontact assembly and which is disposed adjacent one end of saidstationary contact assembly;

c. a corona shield surrounding said stationary contact assembly andhaving an inwardly turned rim at one end thereof which is disposed in aplane which generally includes said one end of said stationarycontactassembly, the inner diameter of said inwardly turned rim beingapproximately equal to the outer diameter of said tubular interrupterassembly, and gas discharge opening means in said inwardly turned rimwhich are radially removed from its said inner diameter;

d. and a high-pressure gas source and conduit means for movinghigh-pressure gas through a generally reentrant path which has a firstleg including said tubular interrupter assembly and said gas dischargechannel in said stationary contact, and a second, and reentrant legincluding said gas discharge opening means in said corona shield; thedischarge of all gas from said gas discharge opening means beingdirecteddown and away from said outer insulation surface of said tubularinterrupter assembly.

6. The interrupter of claim 5 wherein said discharge opening meansconsists of a plurality of spaced openings in said

1. In a gas blast circuit interrupter; said gas blast circuitinterrupter comprising a stationary contact having a central channeltherethrough, a movable contact movable into and out of engagement withrespect to said stationary contact, a source of high-pressure gas, ahollow cylindrical valve of insulation material surrounding said movablecontact and being movable into and out of sealing relation with anannular area surrounding said central channel, means connecting saidsource of high-pressure gas to the interior of said hollow cylindricalvalve, means for moving said hollow cylindrical valve out of sealingrelation with said annular area when said movable contact moves out ofengagement with said stationary contact, whereby a blast of gas isdirected between said movable and stationary contacts and through saidcentral channel in said stationary contact, and a corona shieldcomprising a smoothly curved, generally hollow cylindrical conductivebody surrounding said stationary contact, one end of said corona shieldbeing in a plane generally adjacent the end of said stationary contactand having an inwardly turned rim portion; the improvement whichcomprises gas discharge opening means in said inwardly turned rimportion which are disposed outwardly from the interior diameter of saidrim portion and gas channel means for connecting said central channel insaid stationary contact to said discharge opening means; the dischargepath of all gas discharged through said discharge opening meansextending at an angle to the axis of said hollow cylindrical valve andbeing directed away from the outer surface of said hollow cylindricalvalve.
 2. The interrupter of claim 1 wherein the outer diameter of saidhollow cylindrical valve is about equal to the internal diameter of saidinwardly turned rim portion of said shield.
 3. The interrupter of claim2 wherein said discharge opening means consists of a plurality of spacedopenings in said rim.
 4. The interrupter of claim 2 which includes asecond interrupter of similar construction positioned adjacent thereto,and a tank for receiving said interrupter and said second interrupter;said discharge opening means of the corona shields of said interruptersdefining blast patterns extending generally laterally of a line joiningsaid interrupters to prevent the application of the gas blast of one ofsaid interrupters to the hollow movable valve of the other.
 5. In ahigh-voltage gas blast interrupter; a. a stationary contact assemblyhaving a gas discharge channel therethrough; b. a tubular interrupterassembly presenting an outer insulation surface which is coaxial withsaid gas discharge channel in said stationary contact assembly and whichis disposed adjacent one end of said stationary contact assembly; c. acorona shield surrounding said stationary contact assembly and having aninwardly turned rim at one end thereof which is disposed in a planewhich generally includes said one end of said stationary contactassembly, the inner diameter of said inwardly turned rim beingapproximately equal to the outer diameter of said tubular interrupterassembly, and gas discharge opening means in said inwardly turned rimwhich are radially removed from its said inner diameter; d. and ahigh-pressure gas source and conduit means for moving high-pressure gasthrough a generally reentrant path which has a first leg including saidtubular interrupter assembly and said gas discharge channel in saidstationary contact, and a second, and rEentrant leg including said gasdischarge opening means in said corona shield; the discharge of all gasfrom said gas discharge opening means being directed down and away fromsaid outer insulation surface of said tubular interrupter assembly. 6.The interrupter of claim 5 wherein said discharge opening means consistsof a plurality of spaced openings in said rim.
 7. The interrupter ofclaim 5 which includes a second interrupter of similar constructionpositioned adjacent thereto, and a tank for receiving said interrupterand said second interrupter; said discharge opening means of the coronashields of said interrupters defining blast patterns extending generallylaterally of a line joining said interrupters to prevent the applicationof the gas blast of one of said interrupters to the hollow movable valveof the other.